1. Field of the Invention
Embodiments of the present invention relate to a recording and/or reproducing optimization methods, media, and apparatuses, and more particularly, to a hard disk drive method, medium, and apparatus optimizing the number and gains of repeatable run-out (RRO) compensators.
2. Description of the Related Art
Various repeatable run-out (RRO) compensation techniques have been conventionally implemented, including those disclosed in Japanese Patent Laid-open Publication No. hei 15-249045, U.S. Patent Publication Nos. 2003-0058569 and 2003-112545, for example.
In general, hard disk drives, are a type of data storage device the that contributes to the operation of a computer system by reproducing data from a disc and/or writing data to the disc using a magnetic head. With increasingly high capacity, high density, and compact structures of hard disk drives, a bit per inch (BPI) indicating a density in a rotating direction of a disk and a track per inch (TPI) indicating a density in a radial direction thereof have also been increasing. As a result, controlling mechanisms with finer control capabilities are desired.
As the recording densities of hard disk drives increase, the number of tracks, for example, on a magnetic disk also gradually increases, which results in an increasing ratio of time required for recording servo information on a magnetic disk compared to the time spent manufacturing the hard disk drive, i.e., during the overall manufacture of the hard disk drive additional time is consistently being required to record servo information on the corresponding magnetic disk.
In order to solve this problem, a new hard disk drive assembly method, called an offline servo track write (STR) method, has been developed. In the offline STR method, a disk is installed in the hard disk drive after, rather than before, recording servo information thereon.
The offline STR method, however, may cause the aforementioned repeatable run-out (RRO) and thus may distort a position error signal (PES), unless the center of the disk is precisely centrally aligned with the center of the spindle motor when the disk is installed in the hard disk drive.
In order to compensate for the RRO, an RRO compensation circuit has been developed. An RRO compensation circuit can include a plurality of RRO compensators, such as a 1× RRO compensator, a 2× RRO compensator, . . . , an NX RRO compensator.
Generally, the RRO may vary depending on an assembled state of the hard disk drive and may differ from portion to portion of the disk installed in the hard disk drive.
Conventionally, however, the number and gains of RRO compensators have been assigned without considering the assembled state of the hard disk drive or the position on the disk in the hard disk drive, thereby making it almost impossible to compensate for the RRO of a PES, and eventually making servo control unstable.
In other words, when the number of RRO compensators is assigned without considering the position of the disk in the hard disk drive, the RRO along an inner portion of the disk may be under-compensated for, whereas the RRO along an outer portion of the disk may be over-compensated for. Thus, a high frequency band of a PES may be unnecessarily amplified making it impossible to precisely compensate for the RRO of the PES.
Particularly, if a fixed number of RRO compensators and a fixed level of gain is adopted, when recording final servo patterns on a reference disk on which a reference pattern has been recorded offline, in the aforementioned self servo recording method, the RRO cannot be successfully compensated for, resulting in servo control becoming unstable.